## Note: There are risks associated with BIOS updates. Follow this process at your own peril. ##

1. Create a DOS bootable USB stick on your Windows computer
1a] Download USBDOS tools from the end of this guide.
1b] Unzip and run HPUSBFW with a spare/empty USB stick plugged in. Select 'Fat32' & 'Create a DOS startup disk', and point the 'Using DOS system files' to a systemfiles folder wherever you unzipped USBDOS.zip. I used WinMe, but either will work.
1c] Download the BIOS update utility from Dell (select DOS Version) and save it to your USB stick: Drivers & Downloads

2. Flash your BIOS
2a] Make sure your Mini 10v is plugged in to power.
2b] Boot the Mini 10v from USB stick.
2c] Run the BIOS update utility by typing the file name and then the force options - in my case "R225278.exe /forceit /forcetype" (without quotes)
2d] The utility will run, beeping loudly (!do not try this in the middle of the night or when wife's favourite TV show is playing nearby!) for several minutes while displaying progress.
2e] System will reboot. If successful, you now have A04 BIOS. If not, you now have a borked Mini 10v. May I suggest... doorstop? :-P

Edit: It turns out that although the HPUSBFW supports a wide variety of USB sticks, some have incompatible chips. In that case, you can try the MKBT (2nd) method from here:
Creating A DOS Bootable USB Key (The Easy Way) - Dashken's I-Blog